Pyrochlore-structured titanate ceramics for immobilisation of actinides: Hot isostatic pressing (HIPing) and stainless steel/waste form interactions

Development of brannerite glass‐ceramics for the immobilization of actinide‐rich radioactive wastes

“…Consequently, borosilicate glass has been extensively investigated as the most popular medium for dealing with reprocessed HLWs . As the second generation waste form, synthetic rock (Synroc) which was first developed in the late 1970s for the immobilization of HLWs from Purex‐type reprocessing of spent nuclear fuels is based on a group of geochemically stable natural titanate minerals which have been shown to be able to lock up uranium and thorium in the natural geological environment for billions of years . Initial Synroc variations were based on Synroc‐C formulation in which zirconolite (CaZrTi 2 O 7 ) and perovskite (CaTiO 3 ) accommodate actinides, Sr and rare earth fission products; hollandite [Ba(Al,Ti) 2 Ti 6 O 16 ] incorporates Cs and Rb, while other fission products such as Tc, Ru, Rh, Pd, etc., form very fine metal particles.…”

“…Initial Synroc variations were based on Synroc‐C formulation in which zirconolite (CaZrTi 2 O 7 ) and perovskite (CaTiO 3 ) accommodate actinides, Sr and rare earth fission products; hollandite [Ba(Al,Ti) 2 Ti 6 O 16 ] incorporates Cs and Rb, while other fission products such as Tc, Ru, Rh, Pd, etc., form very fine metal particles. In the early 1990s, both zirconolite‐ and pyrochlore‐rich (CaATi 2 O 7 , A=actinides) formulations were also developed for the immobilization of various actinide‐rich radioactive wastes including surplus plutonium …”

“…[2][3][4][5] As the second generation waste form, synthetic rock (Synroc) which was first developed in the late 1970s for the immobilization of HLWs from Purex-type reprocessing of spent nuclear fuels [6][7][8] is based on a group of geochemically stable natural titanate minerals which have been shown to be able to lock up uranium and thorium in the natural geological environment for billions of years. [6][7][8][9][10][11][12][13][14][15][16] Initial Synroc variations were based on Synroc-C formulation in which zirconolite (CaZrTi 2 O 7 ) and perovskite (CaTiO 3 ) accommodate actinides, Sr and rare earth fission products; hollandite [Ba (Al,Ti) 2 Ti 6 O 16 ] incorporates Cs and Rb, while other fission products such as Tc, Ru, Rh, Pd, etc., form very fine metal particles. In the early 1990s, both zirconolite-and pyrochlore-rich (CaATi 2 O 7 , A=actinides) formulations were also developed for the immobilization of various actinide-rich radioactive wastes including surplus plutonium.…”

Crystal Chemistry and Structures of (Ca,U) Titanate Pyrochlores

“…T HERE has been a renewed interest in the use of ceramics for the stabilization of long-lived waste isotopes from nuclear power and weapons programs. In particular, ceramics consisting mainly of a pyrochlore-structured titanate [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] were chosen by the U.S. Department of Energy for the immobilization of surplus impure Pu in the U.S. and Russia in the late 1990s. 16 While it has been subsequently argued 17 that pyrochlore-structured zirconates have much more structural resistance to radiation damage arising from the decay of the actinides in the structure than titanate pyrochlores, the zirconates require firing at considerably higher temperatures than the titanates and are much less amenable for the incorporation of the impurities in the surplus Pu.…”

Thermal Conversion of Cs-exchanged IONSIV IE-911 into a Novel Caesium Ceramic Wasteform by Hot Isostatic Pressing

“…It has been widely studied for nuclear waste treatment for more than fifteen years [6][7][8][9][10] and offers several advantages over heating powders or pressed pellets. After HIPing, internal pores and defects within a solid body collapse, as a consequence a homogeneous material with a uniform grain size and a nearly 100% density is achieved.…”